Longhorn cattle and Hungarian pigs to rescue rare butterfly on Exmoor

In the aid of the endangered High Brown Fritillary, Longhorns and Mangalista pigs will be creating potential breeding habitat by ‘mowing’ through Exmoor.

Mangalista pigs

The High Brown Fritillary (Argynnis adippe) is Britain’s most threatened butterfly. Since 1978, this pretty orange butterfly with black chequered wings has declined by 65% in population and 87% in distribution across the UK. Once widespread across England and Wales, their dramatic decline is largely due to destruction of its habitat for development and changes in land management practices. Today, it’s found in just three locations in England, one of which is the sun-bathed Heddon Valley near Barnstaple.

The High Brown Fritillary has a wing span up to 67mm – among the biggest in the UK. Its distinctive caterpillars, covered in spikes, are perfectly camouflaged in dry brown leaf litter in April and May, while the showy adults appear in June and July and drink nectar from thistles and bramble flowers.

With the help of the hairy Hungarian Mangalista hogs and Longhorn cattle, a Butterfly Conservation and National Trust team are working to save the UK’s most endangered butterfly. The south-facing bracken-covered slopes offer ideal breeding conditions for the High Brown, but high-growing trees and shrubs have quickly taken over its habitat.

Acting as living lawnmowers, the hairy chompers are expected to eat their way through the aggressive growth to create space for the delicate Common Dog-violets, which are the High Brown caterpillars’ sole food plant. The conservation team have collected seeds from the Common Dog-violets, which have been germinated in an off-site nursery, and hope to plant them in the subsequent new locations to increase the extent of potential breeding habitat.

Butterfly Conservation Project Officer Ellie Wyatt said: “This is an incredibly exciting project and working with the National Trust is very rewarding. The trust have been working with the pigs for a couple of years and noticed how their rootling actions benefited the soil and encouraged violets to germinate, so it’s great to continue this work to help save the High Brown Fritillary. The Longhorn cattle are also gorgeous and look majestic in the landscape and I’m looking forward to seeing the trails they and the pigs make through the bracken and seeing if violets spring up in these paths. From the pigs to the pollarding woodland work, it’s an innovative project to be part of and I feel honoured to be working with so many passionate people to help this rare butterfly.”

National Trust ranger for West Exmoor Mathieu Burtschell said: “Collaborating with butterfly conservation has allowed us to do some exciting and much needed work in our woodlands that will benefit the High Brown Fritillary as well as many other species. Most of our wooded valleys on West Exmoor were exploited for oak timber and were cyclically clear felled. This industrial exploitation ended about hundred years ago, and the oak trees were allowed to get away. The issue we now have is that most of the trees are the same species, same age, and featureless. The woodland work we are carrying out aims to diversify the structure of this oak monoculture. We have created a series of glade by felling, pollarding (felling above the reach of browsing animals), and ringbarking (leaving trees as standing deadwood). These interventions will allow light in the woodland which will increase the ground flora interest of the site, and add some complexity to the structure of the woodland.”

Butterfly Conservation has identified 10 other National Trust sites where new colonies of High Brown Fritillary could establish and is appealing for donations to support the project. They are training National Trust workers to maintain these precious habitats long into the future, but are also looking for more volunteers to help – contact ewyatt@butterfly-conservation.org for details on volunteering.